Switch for vibratory inverters



Jan. 28, 1941. F. SCHILGEN El AL 2,229,676

SWITCH FOR VIBRATORY INVERTERS Filed June 7, 1939 M p U F I J- 5 [2 J 2 .5 T

v o V LF [D LEI E BY A TORNEY.

Patented Jan. 28, 1941 UNITED STATES PATENT OFFICE SWITCH FOR VIBRATORY INVERTERS Application June 7, 1939, Serial No. 277,866 In Germany June 27, 1938 3 Claims.

This .invention is concerned with vibratory inverters or choppers of the kind used for changing direct current into alternating current, especially for car receivers and the like.

It has been found that when vibratory inverters or choppers of this kind are cut in circuit, there arise comparatively heavy currents and arcing. While it is true that the arcing currents mostly drop within a fraction of a second to normal or disappear entirely, they reduce the practical life of the contacts appreciably; This action will be particularly pronounced whenever the vibratory inverter is united with the primary winding of the transformer, that is to say, a working resistance of low ohmic value. It will occur regardless of whether the control of the current flowing through the energizing magnet for the vibratory or oscillating spring is insured by the.

very working contact or whether a distinct exciting terminal is provided, that is to say, a contact which forms together with the solenoid an exciting circuit independent of the load circuit.

According to the present invention, this drawback is obviated by so designing the switch turn- 2 ing' on the direct current source with which the vibratory inverter is connected that, upon closure of the circuit it is first the distinct exciting circuit which is connected and only later the load.

The advantage of the invention is that the load, that is to say, the working circuit is, by positively acting means, connected onlyafter the exciting circuit has been closed for a brief moment and when the spring has assumed fully the vibrating state. The speed at which the working contacts are severed will, at that instant, have already become so high that the above mentioned arcing which tends to extend the closing times with the resultant production of excess currents, will no longer be able to arise. As a consequence, the actual life of the contacts is prolonged, without the user being called upon to manipulate additional switch means.

In the drawing accompanying the specification, Fig. 1 illustrates diagrammatically a vibratory inverter incorporating the features of the present invention; and, Fig. 2 illustrates a detail of the switching device according to the invention.

In the exemplified embodiment of the invention 50 shown in Fig. 1, the two outer ends of the primary winding of the step-up transformer T by way of the contacts KI and K2 and the leaf spring F interposed between said contacts are alternately connected with the positive pole of the direct ourrent source of potential supply Q. The negative pole of the source of voltage, when switch SI is in the closed state, is connected by way of the slider A and contact P2 with the center tap of the primary winding. To produce and maintain the oscillation of spring F there is provided a distinct 5 exciting contact E which, as basically known in the art, is connected in series with the winding of the exciter magnet M and the voltage source Q. However, for connecting the exciting circuit an accessory terminal PI is provided in the switch S. 10 It is this latter contact or terminal, which, as the wiper A (shown in the ofi position) is rotated,

is the first to be connected with the negative pole of the voltage source, with the result that the exciting circuit is closed and the spring begins to 15 vibrate. It is only after continued rotation of the slide contact that also the terminal P2 becomes connected with the voltage source, with the result that the working circuit is then completed. The slider A is so constructed that in this 20 switch position the exciting circuit stays closed.

The geometrical arrangement of the switch is preferably so that in a positive manner the closing of the working circuit is accomplished only about one-fifth of a second after the closing of the exciting circuit. .In fact, practical experience has shown that the spring practically has assumed the state of full vibration inside this interval of time. To this end, the terminal marked PI is shifted in referenceto normal position'an angle of around 90 degrees, While terminal P2 is shifted in reference to pole Pi another angle of 180 degrees. The user is thus compelled, when in.

the center position, to change his grip, and this precludes the chances of an unduly rapid change from the middle position to the end position. It

is, moreover, suitable to provide notches or arrester points in the three switch positions. The position of the lever of the switch (which may be of the tog le or tommy type) in the three switch positions is indicated in Fig. 2. A stop should also be provided to prevent the risk of the switch being shifted from the ofi point to the end position without passing through the central position in which position merely the exciting circuit is closed.

With the output terminals U and V of the vibratory inverter or chopper may be connected, for instance, a rectifier.

We claim:

1. In a vibratory inverter of the type which includes a vibrating reed driven by an exciting coil, 9. switch for connecting the inverter between a source of operating current and a load, said switch being arranged so that on closure thereof it connects the exciting coil across said source of current just prior to the connection of the source of current to the load to thereby establish substantially normal operation of the vibrating reed prior to connection of the source to the load.

2. In an inverter device, a transformer havin a pair of input terminals and a pair of output terminals, a vibrating reed assembly including a pair of contact elements, said vibrating reed assembly acting in operation to periodically make and break contact with said pair of terminals, means connecting one of said contact elements to one of the transformer input terminals, an exciting coil for said vibrating reed, means for connecting the other contact element to one end of said exciting coil, a pair of primary terminals across which is adapted to be connected a source of primary current, means connecting one of said primary terminals to said vibrating reed, operable switching means for connecting other primary terminal to the. other end of said excitin coil and to the other transformer input terminal, said switching means being arranged so that on closure thereof it first connects said other end of the exciting coil to said other primary terminal and thereafter connects said other transformer input terminal to said other primary terminal.-

3. The vibratory inverter described in claim 1 characterized by that the switch is arranged so that the delay between the connection of the load to the source and the exciting coil to the sourceis of the order of one-fifth of a second.

FRIEDRICH SCHILGEN. ALFRED LEIFER. 

